颞叶癫癎的头皮和深部电极脑电发作期特点

目的：探讨手术治愈和基本治愈的颞叶癫癎（TLE）患者发作期头皮脑电图（EEG）和深部电极EEG的特点.方法：对25例立体定向射频热凝毁损颞叶内侧结构或常规手术切除后随访12月以上,Engel Ⅰ级（临床治愈）者21例和EngelⅡ级（临床基本治愈）者4例（共25例）的发作期头皮EEG和深部电极发作期特点进行分析.结果：头皮EEG描记时逢临床发作者19例,其中EEG为局限的5～13 Hz的典型阵发性节律波者10例,14～20 Hz的快波者4例,局限的2～5 Hz的正弦节律波者3例,EEG呈平坦化2例;深部EEG描记已临床发作者6例,均有15～6 Hz的节律波发放.结论：对于TLE头皮EEG对大多数发作能提供发作起始参考,对于EEG平坦化者需参考其它临床资料;深部电极EEG发作期脑电起始形式比较单一.     

头皮脑电图继发双侧同步(癎)样放电的特点及其临床意义

目的:探讨局灶性癫(癎)患者头皮脑电图(EEG)上继发双侧同步(癎)样放电(SBSD)的表现特点及临床意义.方法:回顾性地分析自2002年3月至2006年3月,于我研究所接受治疗的所有局灶性癫(癎)患者的EEG资料,排除所有颞叶癫(癎),共32例患者的术前EEG上均存在SBSD表现.对这些患者的发作间期与发作期EEG结果进行分析研究.结果:32例患者中,SBSD起源于额区者20例,枕区者10例,顶区者2例.SBSD可表现为棘或尖波、棘慢复合波与快节律三种类型,以棘慢复合波最为常见,占63%.SBSD发作间期较为常见的特点是双侧存在时间差,SBSD始于EEG局灶性异常改变以及局限性慢波一侧;53%的病人发作期EEG表现为局灶性起源.结论:SBSD在局灶性癫(癎)患者中并不少见,而且以额叶最为常见.通过分析SBSD波形的各个特点,有助于判断SBSD原发灶侧别,并与全面性癫(癎)相鉴别,对癫(癎)外科的术前评估具有非常重要的临床意义.     

脑电图在大脑半球切除术前后表现及临床意义

目的:探讨半球综合征(Hemispheric syndromes,HS)患者病变半球切除术前后发作间期与发作期的脑电图(EEG)表现特点及其临床意义。方法:总结自2001年4月至2004年4月行大脑半球切除手术的4例患者的临床资料并结合脑磁共振成像(MRI),对其发作间期、发作期以及病损大脑半球切除术半年后复查EEG结果进行分析总结。结果:4例患者MRI均显示为一侧半球广泛病变,对侧正常。EEG均表现为两侧不对称,患侧波幅明显减低。其中3例EEG表现出背景抑制。发作间期癫 癎异常波表现:1例癎样放电出现的侧别与影像学检查结果相反,2例患者出现了双侧同步癎样放电,1 例无明显异常波。发作期EEG表现:1例患者癎样放电起源与病灶侧别相符,其余3例出现在病灶的对侧。所有患者均接受了病灶侧大脑半球切除术,术后随访最短1例为12个月,4例均没有癫癎发作。手术半年后复查EEG,2例患者对侧发作间期癎样放电未消失,2例对侧EEG正常。结论:EEG对HS患者手术前定位诊断及预后判断都有一定的价值。分析HS头皮EEG时,要考虑到两侧大脑结构的绝对不对称性;当出现双侧癫癎异常放电时,不排除手术可以获得良好预后的可能性,可考虑对患侧半球行切除术治疗。EEG发作期单侧起源,在HS患者癫癎灶定位方面,与MRI结果相比,价值有限。HS患者,如明确患侧已不存在重要功能,应尽早手术治疗。     

Application of correlation dimension and pointwise dimension for non-linear topographical analysis of focal onset seizures

For many patients who are candidates for epilepsy surgery, non-invasive evaluation fails to provide sufficient information to permit surgical treatment. Since there are also definite risks and considerable costs associated with invasive procedures, new (non-invasive) techniques are required. This study provides empirical evidence that a non-linear approach applied to ictal surface electroencephalograms (EEGs) can help to delineate the area of seizure onset and may prove useful in complementing visual analysis of the EEG. Multichannel EEGs, recorded from eight patients with different drug-resistant localisation-related epilepsies, were analysed using the concept of correlation dimension and two extensions based on the pointwise dimension. The latter also provided results in cases where assessment of the correlation dimension was not feasible. Comparative values between 2 and 6 were accepted as the result of the algorithms, mostly 3-4 for the EEG channels strongly reflecting epileptic activity, and 4-6 for the other signals. The proportion of accepted pointwise values was usually 200-800% for strong epileptic EEG activity compared to the other data. The approach permitted the characterisation of the scalp area reflecting epileptic activity. The results obtained were in perfect concordance with those obtained during pre-surgical work-up and confirmed by the post-operative outcome.     

Equivalent dipole estimation of spontaneous EEG alpha activity: two-moving dipole approach

A method of estimating equivalent moving and fixed dipoles from the scalp-recorded EEG alpha waves, with the realistic geometry of the head taken into account, is presented. Twenty-one silver electrodes were used to collect spontaneous EEG alpha waves on the scale. Four models, the single-moving dipole model, the single-fixed dipole model, the two-moving dipole model and the two-fixed dipole model were applied to approximate the EEG alpha field on the scalp. The algorithm, based on a least-squares fit for estimating the moving and the fixed dipoles by using a realistically shaped head model, is described. The numerical accuracy of the algorithm is also evaluated by a computer simulation. It is found that the spontaneous EEG alpha activity observed on the scalp can be represented by two equivalent moving dipoles, simultaneously located separately in the occipital regions of the right and the left hemisphere, at a depth of 4–6 cm beneath the scalp, with a goodness-of-fit of up to 97 per cent for all subjects examined. The excellent fit of the two-moving dipole model to the EEG human alpha activity is also compared with the single-dipole fit.     

Application of correlation dimension and pointwise dimension for non-linear topographical analysis of focal onset seizures

For many patients who are candidates for epilepsy surgery, non-invasive evaluation fails to provide sufficient information to permit surgical treatment. Since there are also definite risks and considerable costs associated with invasive procedures, new (non-invasive) techniques are required. This study provides empirical evidence that a non-linear approach applied to ictal surface electroencephalograms (EEGs) can help to delineate the area of seizure onset and may prove useful in complementing visual analysis of the EEG. Multichannel EEGs, recorded from eight patients with different drug-resistant localisation-related epilepsies, were analysed using the concept of correlation dimension and two extensions based on the pointwise dimension. The latter also provided results in cases where assessment of the correlation dimension was not feasible. Comparative values between 2 and 6 were accepted as the result of the algorithms, mostly 3–4 for the EEG channels strongly reflecting epileptic activity, and 4–6 for the other signals. The proportion of accepted pointwise values was usually 200–800% for strong epileptic EEG activity compared to the other data. The approach permitted the characterisation of the scalp area reflecting epileptic activity. The results obtained were in perfect concordance with those obtained during pre-surgical work-up and confirmed by the post-operative outcome.     

Ictal dipole source analysis based on a realistic scalp-skull-brain head model in localizing the epileptogenic zone

The objective of this study is to examine whether dipole modeling based on a realistic scalp-skull-brain head model (SSB/DT) is useful to localize the epileptogenic zone. Eight patients with surgically treated temporal lobe epilepsy were studied. Dipole locations and vector moments of ictal epileptiform activities were calculated by inverse solution methods. Accuracy of dipole locations were assessed by comparing with intracranial EEG. The patterns of ictal epileptiform activities were correlated with the dipole location and vector moment. Dipole locations of the peaks of ictal epileptiform activities estimated by SSB/DT showed good agreement with the epileptogenic foci determined by intracranial EEG. SSB/DT was able to discriminate between medial and lateral temporal epileptogenic foci. Two distinctive types of dipole vector moments, vertical and horizontal were noted. Vertical dipole vector moments corresponded to the medial temporal dipole source and horizontal dipole vector moments were corresponded to the lateral temporal dipole source. Useful clues to differentiate between medial and lateral temporal lobe epilepsy by the visual inspection of scalp EEG were found. SSB/DT is useful tool in the presurgical evaluation of patients with intractable epilepsy.     

Phase Spectral Analysis of EEG Signals

A new method of phase spectral analysis of EEG is proposed for the comparative analysis of phase spectra between normal EEG and epileptic EEG signals based on the wavelet decomposition technique. By using multiscale wavelet decomposition, the original EEGs are mapped to an orthogonal wavelet space, such that the variations of phase can be observed at multiscale. It is found that the phase (and phase difference) spectra of normal EEGs are distinct from that of epileptic EEGs. That is the variations of phase (and phase difference) of normal EEGs have a distinct periodic pattern with the electrical activity proceeds in the brain, but do not the epileptic EEGs. For epileptic EEGs, only at those transient points, the phase variations are obvious. In order to verify these results with the observational data, the phase variations of EEGs in principal component space are observed and found that, the features of phase spectra is in correspondence with that the wavelet space. These results make it possible to view the behavior of EEG rhythms as a dynamic spectrum.     

Localization of fast MEG waves in patients with brain tumors and epilepsy

It was investigated if single dipole analysis of spontaneous fast waves (>8 Hz) can be used to determine the location of the epileptic focus. Automatic dipole analysis was applied to MEG data of 25 patients with intracranial tumors and epilepsy. The frequency range of 8-50 Hz was divided into standard EEG bands. MEG results were overlaid on the MRI scans of the patients. Dipoles describing fast wave fields were located in the parietal/occipital cortex, and not at tumor border zones. In the cases that the dipoles were lateralized there was no clear preference to be located ipsi or contralateral to the tumor. However the generators of epileptic activity in these patients are thought to be located in the border areas of the tumors. Therefore it seems unlikely that the dipole locations describing fast waves are related to the epileptic zones in patients with brain tumors and epilepsy. A remarkable finding is that lateralized dipoles tend to be located in the right hemisphere and not in the left hemisphere. This appears to reflect an asymmetry of possibly normal background activity.     

后头部癫癎发作症状学与头皮脑电图学分析

目的：研究后头部癫癎（PCE）患者发作症状学及头皮脑电图学（EEG）特点,结合神经影像学探讨PCE诊断要点。方法：回顾性分析在清华大学玉泉医院神经外科5病区（癫癎研究中心）就诊的22例PCE患者的81次发作,分析发作症状学、发作间期与发作期头皮EEG及神经影像学特点,总结诊断要点。结果：22例患者中10例存在影像学异常,后头部发作容易传播而表现为额叶的症状（姿势性不对称强直阵挛等）或颞叶内侧症状（口咽部或肢体自动症）而导致错误的诊断,先兆常常提示发作起源部位,头皮EEG发作间期及发作期往往不能提供明确或正确的信息。结论：PCE发作容易传播而表现为额叶或颞叶内侧症状而导致错误的诊断,先兆常常有助于正确诊断。     

Comparison of performance of spherical and realistic head models in dipole localization from noisy EEG

The performance of a three-shell spherical head model versus the performance of a realistic head model is investigated when solving the inverse problem with a single dipole, in the presence of noise. This is evaluated by calculating the average dipole location error for 1000 noisy scalp potential sets, originating from the same test dipole and having the same noise level. The average location errors are obtained utilizing a local linearization, which is validated with a Monte-Carlo simulation. When the difference between the average location error utilizing a spherical and a realistic head model, represented by deltaR, is large for a large number of test dipoles, then it is worth using the more computationally demanding realistic head model. However, if deltaR is small for a large number of test dipoles, then it does not matter which model is used. For 27 electrodes, an electroencephalogram (EEG) epoch of one time sample and spatially white Gaussian noise, we found that the importance of the realistic head model over the spherical head model reduces by increasing the noise level. We further found that increasing the number of scalp electrodes from 27 to 44 has limited impact on the importance of the realistic head model over the spherical head model in EEG dipole source analysis. By increasing the number of time samples to six, the performance of the realistic head model in the inverse calculation gains importance compared with the three-shell spherical head model. Finally, we used spatially and temporally correlated background EEG instead of Gaussian noise. The advantage of the realistic head model over the spherical head model is reduced when applying correlated noise compared to Gaussian noise.     

Dipole tracing in childhood epilepsy with special reference to Rolandic epilepsy

To assess the clinical applicability of dipole tracing in childhood epilepsy, the location and stability of electric source generator of focal spikes seen in EEG of epileptic children were investigated using this method. The patients were divided into 3 groups; benign childhood epilepsy with centrotemporal spikes (BCECS, Group A, n = 14), other types of epilepsy with centrotemporal spikes (Group B, n = 15) and epilepsy with focal spikes in other areas (Group C, n = 13). The spike dipole in each group was analyzed using dipole tracing method. The following results were obtained. (1) The spikes of BCECS were characterized by constantly stable dipoles, compared to those of the other types of childhood epilepsy. The spikes of epileptic children with mental retardation mostly lacked the stability of dipoles. These seemed to suggest that the stability of dipoles was closely related to the prognosis and pathophysiology of epilepsy. (2) The dipoles of BCECS were localized strictly in the Rolandic area. Dipole tracing from EEG spikes was considered to contribute to the elucidation of the pathophysiology of childhood epilepsy.     

Identification of the visual motion area (area V5) in the human brain by dipole source analysis

The retinal periphery of nine healthy subjects was stimulated with computer-generated random-dot kinematograms. These stimuli provided almost isolated visual motion information and minimal position cues. Pattern-reversal stimuli at the same location in the visual field were used for control. Stimulus-related electrical brain activity was recorded from 29 scalp electrodes. Total mean and individual data were analyzed with a spatiotemporal multiple dipole model. The scalp potentials showed a different spatial distribution for motion and pattern stimulation in the time range of 160–200 ms. In this epoch, the predominant motion-related source activity was localized in the region of the contralateral occipital-temporal-parietal border. A significant ipsilateral source activity was not found. The predominant source activity related to the pattern stimulus occurred in the same epoch. The corresponding equivalent dipole was localized more medially and deeper in the brain. The orientation of these major dipole activities was markedly different. These dipoles appeared to represent activity of distinct extrastriate areas, in contrast to earlier activity which was modelled by more posterior dipoles in the occipital lobe. The latter dipoles were at comparable contralateral locations and had similar peak activities around 100 ms, suggesting an origin in the striate cortex.     

癫痫性痉挛发作的头皮及颅内脑电图特点

目的：研究难治性癫痫性痉挛发作患者的头皮及颅内脑电图（EEG）特点,探讨与痉挛发作相关的EEG变化及其与发作间期放电、神经影像学之间的关系。方法：回顾性分析经外科手术治疗的11例患者的临床资料,分析头皮同步视频脑电图（V-EEG）。此11例患者均行术中皮层EEG监测30～60min,其中4例术前行颅内电极长程EEG监测。结果：8例患者表现为双侧基本对称的痉挛发作,发作期头皮EEG为全导高波幅慢波、尖波伴低波幅快波活动或广泛低波幅快波活动发放;另3例患者表现为一侧肢体的痉挛发作,EEG为局灶性棘慢波发放。术中皮层监测5例患者为反复的、暴发出现的多棘波活动,2例患者见持续性的棘波、尖波活动,4例未见明显的癫痫样电活动。4例行颅内电极监测者发作期EEG表现,2例为“前导性”的高波幅棘波伴随20Hz左右的低波幅快波发放;另2例为局灶性低波幅快波活动并迅速扩散,无“前导性棘波”。手术切除“前导性棘波”或反复性、节律性痫样放电的皮层可消除发作。结论：在一部分癫痫性痉挛发作患者,其痉挛发作可能因新皮层局灶的电发放点燃,颅内EEG如果存在前导性的棘波,这个棘波部位可能是促发痉挛发作的点燃灶。完整切除术中监测呈现反复性、节律性痫样放电的皮层可取得较好的手术效果。     

EEG dipole modeling in complex partial epilepsy

Summary Visual inspection and qualitative impressions of clinical EEG abnormalities are being replaced by quantitative characterization of scalp voltage fields and dipole modeling of underlying cerebral sources. Three approaches have been used in the analysis of focal spikes of complex partial epilepsy. 1) Instantaneous, single dipole, inverse solutions for the voltage topography of the spike peak have revealed two distinct equivalent dipole configurations in the brain lobe beneath the negative extreme - radial and oblique (mixed radial and tangential). Only radial dipoles have been found for frontal and fronto-central spikes, while either type have been found for temporal and occipital spike foci. 2) Dipole stability can be assessed by an inspection of sequential instantaneous solutions encompassing the spike complex or by calculating the standard deviation of dipole location (x,y,z) and orientation (elevation, azimuth) parameters during this period. Two-thirds of spike dipoles of the radial type and essentially all of the oblique equivalent dipoles were found to be stable, whereas one-third of the radial dipoles were unstable in position or orientation. 3) Spatio-temporal analysis can identify multiple underlying sources and their potentials. Modeling separate radial and tangential dipoles over the course of the spike has revealed a composite character for spike fields with oblique dipoles and often has defined leads or lags in activity that suggested propagation between infero-mesial and lateral temporal cortex. Correlations with clinical and intracranial EEG data suggest that patients with mesial temporal sclerosis have spikes with oblique and stable equivalent dipoles; patients with discrete cortical lesions have spikes with radial and stable dipoles; patients with extensive or multi-focal cortical insults have spikes with radial and unstable dipoles.     

Epileptic seizure classifications of single-channel scalp EEG data using wavelet-based features and SVM

In this study, wavelet-based features of single-channel scalp EEGs recorded from subjects with intractable seizure are examined for epileptic seizure classification. The wavelet-based features extracted from scalp EEGs are simply based on detail and approximation coefficients obtained from the discrete wavelet transform. Support vector machine (SVM), one of the most commonly used classifiers, is applied to classify vectors of wavelet-based features of scalp EEGs into either seizure or non-seizure class. In patient-based epileptic seizure classification, a training data set used to train SVM classifiers is composed of wavelet-based features of scalp EEGs corresponding to the first epileptic seizure event. Overall, the excellent performance on patient-dependent epileptic seizure classification is obtained with the average accuracy, sensitivity, and specificity of, respectively, 0.9687, 0.7299, and 0.9813. The vector composed of two wavelet-based features of scalp EEGs provide the best performance on patient-dependent epileptic seizure classification in most cases, i.e., 19 cases out of 24. The wavelet-based features corresponding to the 32–64, 8–16, and 4–8 Hz subbands of scalp EEGs are the mostly used features providing the best performance on patient-dependent classification. Furthermore, the performance on both patient-dependent and patient-independent epileptic seizure classifications are also validated using tenfold cross-validation. From the patient-independent epileptic seizure classification validated using tenfold cross-validation, it is shown that the best classification performance is achieved using the wavelet-based features corresponding to the 64–128 and 4–8 Hz subbands of scalp EEGs.     

脑电图在颞叶癫痫伴精神障碍患者中的临床应用

目的 探讨脑电图检查在颞叶癫痫伴精神障碍患者中的临床应用价值。方法 选取2013年6月~2018年7月我院确诊的颞叶癫痫伴精神障碍患者45例,所有患者进行常规脑电图、视频脑电图和蝶骨电极脑电图检查,对比分析其结果。结果 常规脑电图痫样波检出阳性率（24.44%）低于视频脑电图（48.89%）和蝶骨电极脑电图（64.44%）,差异具有统计学意义（P＜0.05）;癫痫样放电以左侧为主,前颞部位多见,定侧率为86.67%、定位率为91.11%;异常放电形式以棘波、尖波为主,5例患者未见癫痫样放电,以颞区θ、δ活动为主;脑电图背景活动异常表现为α节律衰减,β活动、θ和δ活动增加;清醒期患者癫痫波检出率（28.89%）低于睡眠期患者癫痫波检出率（53.33%）,差异有统计学意义（P＜0.05）。结论 颞叶癫痫伴精神障碍患者具有特征性的脑电图表现,背景活动异常、发作间期及发作期异常放电波形与部位等特点对颞叶癫痫的鉴别诊断及临床治疗有重要的临床价值。     

癫癎发作早期Video-EEG监测的临床价值

目的 :探讨Video -EEG监测癫发作早期脑电变化的临床应用价值。方法 :对 96例临床确诊的癫患者进行发作早期Video -EEG监测并分析其结果。结果 :共监测到 3 2例癫发作(3 3 % ) ,其中全身性癫 4例 ;颞叶癫 16例 ,颞外癫 12例。发作早期脑电异常主要分快活动、慢活动及快慢混合活动三大类。根据发作早期脑电变化 ,2 3例 (72 % )作出定位诊断。结论 :癫发作早期脑电图脑电变化对致灶的定位 (定侧 )诊断有重要价值     

Epileptic seizure detection using DWT-based approximate entropy,Shannon entropy and support vector machine: a case study

In this work, we have used a time–frequency domain analysis method called discrete wavelet transform (DWT) technique. This method stand out compared to other proposed methods because of its algorithmic elegance and accuracy. A wavelet is a mathematical function based on time-frequency analysis in signal processing. It is useful particularly because it allows a weak signal to be recovered from a noisy signal without much distortion. A wavelet analysis works by analysing the image and converting it to mathematical function which is decoded by the receiver. Furthermore, we have used Shannon entropy and approximate entropy (ApEn) for extracting the complexities associated with electroencephalographic (EEG) signals. The ApEn is a suitable feature to characterise the EEGs because its value drops suddenly due to excessive synchronous discharge of neurons in the brain during epileptic activity in this study. EEG signals are decomposed into six EEG sub-bands namely D1–D5 and A5 using DWT technique. Non-linear features such as ApEn and Shannon entropy are calculated from these sub-bands and support vector machine classifiers are used for classification purpose. This scheme is tested using EEG data recorded from five healthy subjects and five epileptic patients during the inter-ictal and ictal periods. The data are acquired from University of Bonn, Germany. The proposed method is evaluated through 15 classification problems, and obtained high classification accuracy of 100% for two cases and it indicates the good classifying performance of the proposed method.     

Seeing through the skull: Advanced EEGs use MRIs to accurately measure cortical activity from the scalp

Summary There is a vast amount of untapped spatial information in scalp- recorded EEGs. Measuring this information requires use of many electrodes and application of spatial signal enhancing procedures to reduce blur distortion due to transmission through the skull and other tissues. Recordings with 124 electrodes are now routinely made, and spatial signal enhancing techniques have been developed. The most advanced of these techniques uses information from a subject's MRI to correct blur distortion, in effect providing a measure of the actual cortical potential distribution. Examples of these procedures are presented, including a validation from subdural recordings in an epileptic patient. Examples of equivalent dipole modeling of the somatosensory evoked potential are also presented in which two adjacent fingers are clearly separated. These results demonstrate that EEGs can provide images of superficial cortical electrical activity with spatial detail approaching that of O15 PET scans. Additionally, equivalent dipole modeling with EEGs appears to have the same degree of spatial resolution as that reported for MEGs. Considering that EEG technology costs ten to fifty times less than other brain imaging modalities, that it is completely harmless, and that recordings can be made in naturalistic settings for extended periods of time, a greater investment in advancing EEG technology seems very desirable.Supported by the National Institute of Neurological Diseases and Stroke, the National Institute of Mental Health, the National Institute of Health, the Air Force Office of Scientific Research, the Air Force School of Aerospace Medicine and the Office of Naval Research. Access to neurosurgery patients was kindly provided by the Northern California Comprehensive Epilepsy Center at the University of California (San Francisco), Dr. Kenneth Laxer, Director, and Dr. Nicolas Barbaro, Neurosurgeon. Contributions to the research presented here were also made by our colleagues at EEG Systems Laboratory including Jim Alexander, Brian Cutillo, Judy McLaughlin, and Michael Ward.